They are not.
Possibly, some homeopathic medicines do actually have a physical effect. But most homeopathic medicines are placebos, they work through belief, it doesn't cure the infection but the person taking the medicine feels better because they believe that it is making them better.
Some homeopathic treatments are so diluted that they don't contain any active ingredient.
Another view
When consumed in an infectious disease the medicines stimulates the life force (Vital Force) which in turn attack the bacteria, viruses to cure the illness. Some of the medicines having anti-bacterial action are Curcuma Longa, Einbelia Ribes, etc
Asthma Treatment is possible with Homeopathic Approach, well there are so many thoughts about Homeopathic Treatment. If you can add some views about Ashtma and Respiratory treatment.
Arnica
A hospital which uses Homeopathic medicines rather than conventional medicines for treatment of a patient.
Thorazine
usually minimal side effects. Its non-toxicity makes it a good choice for the treatment of children. Another benefit of homeopathy is the cost of treatments; homeopathic remedies are inexpensive
Homeopathic treatment for acute back pain consists of applications of Arnica oil to the sore area or oral doses of Arnica or Rhus toxicodendron.
virus
The primary risks to the patient from constitutional homeopathic treatment are the symptoms of the healing crisis and individual reactions to homeopathic medicine.
Homeopathic medicine is not used to treat specific named conditions, but is chosen based on the totality of the patient's symptoms.
There have beens everal success stories with homeopathic treatments for cancer. Please find a reputable doctor to help with your treatment.
Symptom similarity indicate the correct medicine
Some homeopathic remedies for treatment of the common cold are Aconite, Belladona, Allium Cepa, Dulcamara, Gelsemium, Hepar Sulph, Nux Vomica, Pulsatilla, and Natrum Mur.